Internal Biasing in Relaxor Ferroelectric Polymer to Enhance the Electrocaloric Effect

The relaxor ferroelectric materials, because of their large and reversible electric field induced polarization, have been demonstrated to possess giant electrocaloric effect (ECE) over a broad temperature range, which are attractive for refrigeration with high energy efficiency and environmental friendliness. However, high electric fields are required to generate the giant ECE in these materials, posing challenge for these materials in practical cooling devices which also require high reliability and low cost. Here, a general approach is reported, for example, establishing an internal bias field in these relaxor ferroelectric polymers, to significantly improve ECE which can be induced at low electric fields. It is demonstrated that in a polymer blend (nanocomposite) with a properly controlled normal ferroelectric in nanophase dispersion in the relaxor polymer matrix, the charge neutrality in the blends can cause an internal biasing field, leading to more than 45% enhancement in the ECE at low electric field (≈50 MV m^-1). This internal biasing approach provides a universal strategy to enhance other low field responses such as the electromechanical response in relaxor ferroelectrics.